2/7 + 3/5

= 10/35 + 21/35  

= 31/35

   31/35 - 2/7  

= 31/35 - 10/35  

= 21/35

= 3/5

   31/35 - 2/5

= 31/35 - 14/35  

= 17/35

   3/5 + 2/7  

= 21/35 + 10/35

= 31/35

2/7 + 3/5 = 10/35 + 21/35 = 31/35

31/35 - 2/7 = 31/35 - 10/35 = 21/35

31/35 - 2/5 = 31/35 - 21/35 = 10/35

3/5 + 2/7 = 21/35 + 10/35 = 31/35

2/7+3/5 =31/35

31/35-2/7=21/35

31/35-2/5=17/35

3/5+2/7=31/35

nhớ tích cho minh nhé mình kb cho mình là con gái

1)  35.18−5.7.28=−350

2)  45−5(12+9)=−60

1) 35.18-5.7.28

=630-5.7.28

= 630-980

=630+(-980)

=-(980-630)

=-350

1) 35 . 18 - 5 . 7 . 28
= 630 - 35 . 28
= 630 - 980
= -350

2) 45 - 5.(12+9)

= 45-5×21

= 45-105

=-60

3) 31. (-18) + 31. ( - 81) – 31

=31.(-18)+31+81+(-31)

=31.(-18)+[31+ -(31)]+81

câu 5 sai nha

1)  

2)  

1) 35.18-5.7.28

=630-5.7.28

= 630-980

=630+(-980)

=-(980-630)

=-350

a) \(6-\dfrac{2}{5}+\dfrac{3}{5}\) x \(3\)

\(=6-\dfrac{2}{5}+\dfrac{9}{5}\)

\(=\dfrac{30}{5}-\dfrac{2}{5}+\dfrac{9}{5}\)

\(=\dfrac{30-2+9}{5}=\dfrac{37}{5}\)

b) \(\left(\dfrac{31}{35}-\dfrac{4}{7}\right)\) x \(\dfrac{8}{7}:2\)

\(=\left(\dfrac{31}{35}-\dfrac{20}{35}\right)\) x \(\dfrac{8}{7}:2\)

\(=\dfrac{11}{35}\) x \(\dfrac{8}{7}:2\)

\(=\dfrac{11}{35}\) x \(\dfrac{8}{7}\) x \(\dfrac{1}{2}\)

\(=\dfrac{\text{11 x 8 x 1}}{\text{ 35 x 7 x 2}}=\dfrac{88}{490}=\dfrac{88}{245}\)  

a) 6−25+356−25+35 x 33

=6−25+95=6−25+95

=305−25+95=305−25+95

=30−2+95=375=30−2+95=375

b) (3135−47)(3135−47) x 87:287:2

=(3135−2035)=(3135−2035) x 87:287:2

=1135=1135 x 8

a: =-3/24-40/24

=-43/24

b: \(=\dfrac{6}{54}\cdot\dfrac{49}{35}=\dfrac{1}{9}\cdot\dfrac{7}{5}=\dfrac{7}{45}\)

c: \(=\dfrac{6}{5}+\dfrac{4}{3}=\dfrac{18+20}{15}=\dfrac{38}{15}\)

d: \(=\dfrac{31}{17}-\dfrac{14}{17}-\dfrac{5}{13}-\dfrac{8}{13}=1-1=0\)

\(\frac{6-2}{5}+\frac{3}{5.3}\)

\(=\frac{4}{5}+\frac{1}{5.1}\)

\(=\frac{4}{5}+\frac{1}{5}\)

\(=\frac{5}{5}=1\)

a. 6 x 3 - ( \(\frac{2}{5}+\frac{3}{5}\)) = 6 x 3 - \(\frac{5}{5}\)= 6 x 3 - 1 = 18 - 1 = 17

b.(  \(\frac{31}{35}-\frac{4}{7}\)) x \(\frac{8}{7}\): 2 =\(\frac{11}{35}\)x \(\frac{8}{7}\): 2 =\(\frac{88}{245}\): 2 = \(\frac{88}{490}\)= \(\frac{44}{245}\)= ...........rút gọn đến khi hết

a) \(6-\frac{2}{5}+\frac{3}{5}\times3\)

\(=6-\frac{2}{5}+\frac{9}{5}\)

\(=\frac{30}{5}-\frac{2}{5}+\frac{9}{5}\)

\(=\frac{28}{5}+\frac{9}{5}\)

\(=\frac{37}{5}\)

b) \(\left(\frac{31}{35}-\frac{4}{7}\right)\times\frac{8}{7}:2\)

\(=\frac{11}{35}\times\frac{8}{7}:2\)

\(=\frac{88}{245}:2\)

\(=\frac{44}{245}\)

bạn lên mạng tra từng câu 1 sẽ có

ukm cảm ơn bạn nhìu

\(\frac{-5}{16}+\frac{7}{12}-\frac{13}{9}\)

\(MSC=BCNN(16,12,9)=144\)

Ta có : \(\frac{-5}{16}+\frac{7}{12}-\frac{13}{9}=\frac{-45}{144}+\frac{84}{144}-\frac{208}{144}=\frac{-45+84-208}{144}=\frac{-169}{144}\)

Bài b tự xử